<!DOCTYPE html>
<html lang="zh-CN">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    .fu {
      /* 父类缩小到,所有的子类内部紧挨边框,不在缩小 */
      display: flex;
      background-color: aqua;
      height: 500px;
      width: 400px;
      flex-direction:row;     
      /* 子类缩小 是否换行 wrap 换行 nowrap 不换行 */
      flex-wrap:wrap;
      /* 设置多行 flex-start,flex-end,center 的居中 space-between 上,下中间均分 space-around 2元素中间双倍 evenly 间距均分 stretch 拉伸 父类等高,多个均分父类高,子类不能有高度设置  */
      align-content: stretch;
    }

    .son {
      border: 1px solid #ccc;
      width: 100px;
    }

    span {
      width: 100px;
      border: 1px solid #ccc;
      
    }
  </style>
</head>

<body>
  <div class="fu">
    <div class="son">div1</div>
    <div class="son">div2</div>
    <div class="son">div3</div>
    <span>我是sapn</span>
  </div>

  <!-- <p>我是p标签</p> -->
</body>

</html>